Robust Adaptive Beamforming with Variable Diagonal Loading

In this paper, we propose an alternative realization of the robust adaptive linearly constraint minimum variance (LCMV) beamforming which including ellipsoidal uncertainty constraint on the steering vector. More specifically, the genuine steering vector is estimated from the presumed steering vector using recursive steepest descent (RSD) algorithm with the ellipsoidal constraint imposed on the estimated steering vector. A diagonal loading technique is obligatory to satisfy the ellipsoidal constraint. The main drawback of the diagonal loading techniques is that it is not clear how to get the optimal value of diagonal loading level based on the recognized level of uncertainty constraint. In this paper, this drawback is tackled whereas the diagonal loading technique is integrated into the adaptive update scheme by means of variable loading (VL) technique rather than fixed diagonal loading or ad hoc techniques.